The invention relates generally to an oscillator for a continuous casting mold.
More particularly, the invention relates to an oscillator of the type which can be remotely adjusted so as to change the oscillation stroke.
In the continuous casting of steel, only a thin layer of steel adjacent to the walls of the mold undergoes solidification in the mold. The continuously cast strand withdrawn from the mold thus consists of a thin outer shell surrounding a molten core. Since the shell is not only thin but is also at a very high temperature, it is relatively weak so that care must be exercised to limit the stress which is applied to the shell in order to withdraw the strand from the mold. Excessive stress will cause the shell to rupture. Rupture of the shell inside the mold is bad for the surface quality of the strand while rupture outside of the mold will result in a breakout, i.e., an escape of the molten core.
The shell has a tendency to stick to the mold. Inasmuch as sticking of the shell to the mold can increase the withdrawal stress sufficiently to cause rupture of the shell, it has become the practice to oscillate or reciprocate the mold during casting. Mold oscillation prevents sticking of the shell to the mold.
Although sticking is prevented by mold oscillation, there is nevertheless friction between the shell and the mold. To avoid rupture of the shell, the friction must not be allowed to become excessive.
The friction between the shell and the mold is affected by a number of factors, e.g., temperature, which can change during a casting operation. The friction is likewise a function of the oscillation stroke. Thus, it is possible to control the friction via the oscillation stroke.
Modern machines for the continuous casting of steel are equipped with instrumentation for indicating the friction between the shell and the mold. These machines are also designed such that the oscillation stroke and frequency can be adjusted. The frequency is remotely adjustable by changing the rpm of the main oscillator motor which may, for example, be achieved by the use of a d.c. motor and related speed controls.
The oscillation stroke in currently available machines is adjustable only when the oscillator drive is at a standstill. The adjustment may be performed manually or remotely but, in either case, requires casting to be stopped thereby resulting in lost production time.